There has been already provided this kind of door locking device by which doors are formed to be opened from both sides, having a rotatable locking bar provided with cams at the upper and lower ends repsectively of the outside surface of each door and cam keepers engaging respectively with the cams at the upper and lower ends of the locking bar above and below an inlet part, that is, a door frame so as to lock the doors by engaging the cam keepers with the cams.
However, such conventional door locking device have defects which make it weak against the end wall load and racking load, and lacking in the durability. In addition this lock requires a large force to open and close the door.